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JGR Space Physics - 2023 - Bower - Formation and Motion of Horse Collar Aurora Events.pdf (4.63 MB)

Formation and Motion of Horse Collar Aurora Events

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posted on 2024-03-05, 16:03 authored by GE Bower, SE Milan, LJ Paxton, E Spanswick, MR Hairston

The polar cap can become teardrop shaped through the poleward expansion of the dusk and dawn sectors of the auroral oval, to form what is called horse collar aurora (HCA). The formation of HCA has been linked to dual-lobe reconnection (DLR) where magnetic flux is closed at the dayside magnetopause. A prolonged period of northward IMF is required for the formation of HCA. HCA have previously been identified in UV images captured by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument on-board the Defense Meteorological Satellite Program (DMSP) spacecraft F16, F17 and F18. Events that have concurrent 630.0 nm all-sky camera (ASC) data from the Redline Geospace Observatory (REGO) Resolute Bay site are now studied in more detail, making use of the higher cadence of the ASC images compared to DMSP/SSUSI. 11 HCA events are studied and classified based on the IMF conditions at the end of the event. Five of the events were found to end via a southward turning of the IMF, two end with positive By dominated IMF and four with negative By dominance. Under positive (negative) By the arcs move duskward (dawnward) in the northern hemisphere with the opposite true in the southern hemisphere. Under a southward turning the arcs move equatorward. One event is of particular interest as it occurred while there was a transpolar arc (TPA) also present. Understanding the evolution of HCA will allow DLR to be studied in more detail.

Funding

A Consolidated Grant Proposal for Solar and Planetary Science at the University of Leicester, 2019 - 2022

Science and Technology Facilities Council

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Norges Forskningsråd

History

Author affiliation

School of Physics & Astronomy, University of Leicester

Version

  • VoR (Version of Record)

Published in

Journal of Geophysical Research: Space Physics

Volume

128

Issue

5

Publisher

American Geophysical Union (AGU)

issn

2169-9380

eissn

2169-9402

Copyright date

2023

Available date

2023-11-08

Language

en

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